The procedure for replacing a faulty disk mechanism depends
on the type of disk configuration you are using. Separate descriptions
are provided for replacing an array mechanism and a disk in a high availability
enclosure.
Replacing
a Lock Disk |
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Replacing a failed lock disk mechanism is the same as replacing
a data disk. If you are using a dedicated lock
disk (one with no user data on it), then you need to issue only
one LVM command, as in the following example:
# vgcfgrestore -n /dev/vg_lock /dev/dsk/c2t3d0 |
Serviceguard checks the lock disk on an hourly basis. After
the vgcfgrestore command, review the syslog file of an active cluster
node for not more than one hour. Then look for a message showing
that the lock disk is healthy again.
On-line
Hardware Maintenance with In-line SCSI Terminator |
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In some shared SCSI bus configurations, on-line SCSI disk
controller hardware repairs can be made if HP in-line terminator
(ILT) cables are used. In-line terminator cables are supported with
most SCSI-2 Fast-Wide configurations.
In-line terminator cables are supported with Ultra2 SCSI host
bus adapters only when used with the SC10 disk enclosure. This is
because the SC10 operates at slower SCSI bus speeds, which are safe
for the use of ILT cables. In-line terminator cables are not supported
for use in any Ultra160 or Ultra3 SCSI configuration, since the
higher SCSI bus speeds can cause silent data corruption when the
ILT cables are used.
The in-line terminator cable is available in a number of form
factors; in each case, the connector at one end contains SCSI termination,
which is used to terminate the end of the SCSI bus instead of the
termination on the SCSI host bus adapter (HBA) in the node. If the
terminated end of an ILT cable is connected to an HBA, then termination
must be disabled on that HBA. Disabling the termination is done
on the HBA by removing the termination resistor packs, setting the
appropriate DIP switches on the HBA, or by programmatically disabling
termination, depending on the HBA being used. (Consult the documentation
for the HBA to see which method works for a particular HBA.)
ILT cables can be used in combination with Y-cables to allow
additional nodes to be connected to the shared SCSI bus. Some SCSI
cables available from HP have combined ILT and Y-cable functionality.
Any nodes connected to the middle connector of a Y-cable must also
have SCSI termination disabled on the HBA’s.
When an ILT cable is used, it is possible to physically disconnect
a host from the end of the shared SCSI bus without breaking the
bus’s termination, allowing the remaining nodes in the
cluster to continue to access the shared SCSI bus while the repairs
are being made.
Similarly, it is possible to physically disconnect a host
from the middle connector of a Y-cable on a shared SCSI bus without
breaking the bus’s termination.
Whether using ILT cables or Y-cables, however, it is strongly recommended
that you do not try to physically reconnect an HBA to the shared
SCSI bus without first halting all nodes connected to that shared SCSI
bus. This is because it is very easy to inadvertently short out
a pin in the connector against the chassis ground, which would damage
the other HBA’s connected to the shared SCSI bus, and bring
the entire SCSI bus down.
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 | NOTE: You cannot use inline terminators with internal FW/SCSI
buses on D and K series systems, and you cannot use the inline terminator
with single-ended SCSI buses. You must not use
an inline terminator to connect a node to a Y cable. |
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Figure 8-1 “F/W
SCSI-2 Buses with In-line Terminators ” shows a three-node
cluster with two F/W SCSI-2 buses. The solid line and the dotted
line represent different buses, both of which have inline terminators
attached to nodes 1 and 3. Y cables are also shown attached to node
2.
The use of in-line SCSI terminators allows you to do hardware maintenance
on a given node by temporarily moving its packages to another node
and then halting the original node while its hardware is serviced.
Following the replacement, the packages can be moved back to the
original node.
Use the following procedure to disconnect a node that is attached
to the bus with an in-line SCSI terminator or with a Y cable:
Move any packages on the node that requires maintenance to
a different node.
Halt the node that requires maintenance. The cluster
will re-form, and activity will continue on other nodes. Packages
on the halted node will switch to other available nodes if they
are configured to switch.
Disconnect the power to the node.
Disconnect the node from the in-line terminator
cable or Y cable if necessary. The other nodes accessing the bus
will encounter no problems as long as the in-line terminator or
Y cable remains connected to the bus.
Replace or upgrade hardware on the node, as needed.
Halt all nodes connected to the shared SCSI bus,
and power them down.
Reconnect the node to the in-line terminator cable
or Y cable if necessary.
Power-on the nodes in the cluster. If AUTOSTART_CMCLD is set to 1 in the /etc/rc.config.d/cmcluster file, the nodes will automatically start the cluster
and the packages.
If necessary, move packages back to the node from
their alternate locations and restart them.
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